Hollow sheet-metal unit



June 3, 1930. A R, GRosg 1,761,037

HOLLOW SHEET METAL UNIT Filed Sept. 15, 1927 Patented June 3,

UNITED STATES PATENT OFFICE I ARTHUR B. GROSS, OF ST. PAUL, MINNESOTA, ASSIGNOR, BY MESNE ASSIGNMENTS, 'I'O TRUSSBILT STEEL DOORS, INO., OF ST. PAUL, MINNESOTA, A CORPORATION OF DELA- WARE noLLow SHEET-METAL um'r Application filed September 15, 1927. Serial No. 219,643.

My present invention relates to a hollow sheet metal unit having an internal metal reinforcement spot welded thereto, and has for its object the provision of such a unit that is l of relatively light weight, strong and rigid.

Said invention has for its further object the elimination or reduction to a minimum the shrinkage, warpage or other distortion 1n its side plates due to heat produced during the 1 spot welding of the metal reinforcement to shape, iseliminated, thus materially red cing the cost of manufacture, and at the sa e time producing a unit that does not require filling by a heavy coat of finishing material such as ,palnt, enamel or the like, to fill the uneven .surfaces thereof in order to -make a smooth exterior finish. Such filling is highly objectionable for the reason that if it cracks, peels, or is otherwise defaced, it is practically impossible to refinish the same properly without sending the same back to the factory, which is very expensive.

The invention, while intended for general use in the construction of table tops, and panels in buildingstructures, car bodies and the like, is especially well adapted in the construction of doors and is so illustrated and described in the present application.

To the above end, generally stated, the invention consists of the novel devices and combinations of devices hereinafter described and defined in the claims.

In the accompanying drawings, which illustrate the invention, like characters indicate like parts throughout the several views.

Referring to the drawings:

Fig. 1 is a View partly in side elevation and-partly in vertical section taken substantially at the transverse center of the door;

. Fig. 2 is an end view of the improved door;

Fig. 3 is a fragmentary view in horizontal section taken on the line 33 of Fig. 1, on an enlarged scale; and

Fig. 4 is a fragmentary transverse vertical section taken on the line 4-4 of Fig. 3.

The numeral 5 indicates a hollow sheet metal unit or door comprising a pair of duplicate laterally spaced plates 6, the longitudinal edge portions of which are bent laterally toward each other and connected by joints 7 to form the longitudinal edgeportions of said door. The ends of the door 5 are closed by channel end pieces 8 fitted therein with their flanges turned outward and spot welded at 9 to the sides of the plates 6. Longitudinal slots are formed in each end of each end piece 8 to aiford liquid-filling and drain holes 10.. These holes 10 also permit the insertion of fastening devices into the door 5 for use in handling the same during the process of treating or finishing the door, as disclosed and broadly claimed in application executed of date August 31, 1927, and entitled Hollow sheet metal units and process of producing the same.

Within the door 5 is a truss structure 11 for the plates 6 and comprises a corrugated sheet metal plate. The apexes 12 of its corrugations are truncated-onflat "and alternately and directly engage the inner faces of the plates 6 and are spot welded thereto at 13.

The apparatus used in spot welding the truss structure 11 to the plates 6 is disclosed and broadly claimed in my co-pendi'ng application entitled Welding apparatus, filedJuly f 2, 1927, under Serial No. 203,236.

The longitudinal edge portions of the truss structure 11 are shaped to form portions of joints 7 and which joints are preferably of the type disclosed and broadl claimed in my co-pending application entit ed Metal door versely oblique, straight and flat in cross section. These'webs afford compression tension members that connect the two plates 6 and will not stretch, straighten or buckle under pressure or strains applied. to the door 5.

As previously stated, the plates 6 are duplicates and their joints 7 are connected by the longitudinal sliding movements of one of the plates 6 in respect to the other. These joints 7 securely hold the plates 6 interlocked against movements in all directions transversel of the door. It is highly important to note that the sheet metal plate from which the truss structure 11 is formed is of a lighter gauge than the two plates 6 and, b referthe same time gives the necessary strength and rigidity to the door- 5 and reduces the weight thereof. The use of a relatively thin metal for the truss structure 11 also has another important function in that it will be heated much quicker than the respective relatively thick plate 6 and hence fuse with the metal in the inner face of said plate to form a spot weld before the outer face of said plate is distorted'to any marked degree by the heat from the contacting electrode av.

The use of the relatively small electrode 3 contacting with the truss structure 11 and the co-operating relatively large electrode at contacting with the plate Gfurther facilitates the heating of'the truss structure 11 faster than the heating of the outer face of the plate 6 for the reason that the current passing through theelectrodey to said truss structure is confined to a much smaller area than. i the current passing through the electrode at to the plate What I claim is: 1. A hollow sheet metal unit comprising a pair of laterally spaced side plates, the longitudinal edge portions of which are shaped to form' the edges of the unit, channel. end pieces fitted into the ends of the unit with their flanges turned outward and spot welded to the sides of the unit, a metal reinforcement in the unit comprising a corrugated metal sheet welded at its apexes to the sides of the unit and affording afplurality at each end of the unit, and liquid-filling and drain holes in the end pieces.

2. A hollow sheet metal unit comprising a pair of laterally spaced sides, the longitudinal edges of which are shaped to form the edges of the unit, channel end ieces fitted into the ends of the unit with t eir flanges i,

' a pair of spaced stifl metal side plates, and an internal reinforcement for said unit comprising a relatively light gauge corrugated metal sheet, the apexes of the corrugations being truncated and fused to the inner surfaces of said side plates and the webs of the corrugations being reversely oblique and straight in cross-section, said corrugated metal sheet being of a sufficiently lighter gauge than the side plates that fusion thereof may be accomplished without altering the outer surface of the side plates, whereby maximum strength and rigidityis effected with the minimum of reinforcing material and surface contact with the side plates.

4. A hollow sheet metal unit comprising a pair of spaced stiif metal side plates and an internal reinforcement for said unit comprising a relatively light gauge corrugated metal sheet fused to the inner surfaces of said'spaced side plates, said corrugated metal sheet being of a sufiiciently lighter gauge than-the side plates that fusion thereof may be accomplished without altering the outer surface 0 the side plates.

5. A hollow sheet metal unit comprising a pair of laterally spaced side plates, the longitudinal edge portions of which are bent laterally and permanently connected together, channeled end pieces closing the ends of the unit, and .a metal reinforcement in the unit spaced from the end pieces and com-.

prising a corrugated metal sheet Welded at its apexes to the sides of the unit providing longitudinally extending tubular sections having communication one with the other adjacent the ends of the unit.

In testimony whereof I aflix my signature. ARTHUR R. GROSS.

of open-ended tubular sections that extend I longitudinally of the unit and terminate short of the end pieces to afford a chamber 

